Screw compressor

ABSTRACT

The invention revealed a screw compressor and its electrical control system and related control methods. The system comprises a power module, a high-low (tension) transformer and a compressor wiring control circuit. The high-low (tension) transformer connects the power module to provide at least two different voltages: low voltage and high voltage; the compressor wiring control circuit connects said high-low (tension) transformer to control the switching and connection mode of said wiring terminals of the compressor; When the first voltage is connected to the screw compressor, the connecting circuit formed by the wiring terminals which are controlled by a connecting unit will be in the first status. When the second voltage is connected to the screw compressor, the connecting circuit formed by the wiring terminals which are controlled by a connecting unit will be in the second status. The electrical control system of the compressor revealed by the invention can easily realize the switching of low and high voltage by changing the jumpers on the wiring terminals of the patch board with no need to change the connection mode of the motor.

FIELD OF THE INVENTION

The electrical control technology adopted in the invention refers to a screw compressor, especially the electrical control system and methods.

BACKGROUND OF THE INVENTION

Air compressors, with so many categories, can be divided into positive displacement compressor and dynamic compressor according to the working principle. The positive displacement compressor can be further divided into reciprocal compressor and rotary compressor. The working principle of positive displacement compressor is to compress the volume of the air which increases the density of gas molecules in unit volume to add the pressure of the compressed air while that of dynamic compressor such as centrifugal compressor is to accelerate the movement speed of gas molecules to transform the dynamic energy of the gas molecules into pressure energy to add the pressure of compressed air.

Screw compressor is one kind of positive displacement compressor, whose air compression is realized by the volume change of the groove of toothing negative-positive rotors in parallel which are set in the cabinet.

The working principle of a screw compressor is as follows:

A pair of spiral toothing negative-positive rotors is set in the air cylinder of the screw compressor. The two rotors with several concave gears rotate reversely to each other. The clearance between the rotors and the rotors and the cabinet is only 0.5˜1 millimeter. The main rotor (positive rotor or negative rotor) is driven by the engine or the motor (motor in most cases) and the other rotor (positive rotor or negative rotor) is driven by the oil film which is formed through oil injection of the main rotor or by the synchronized gears of the main rotor and concave rotor. Therefore, metal touch does not occur during the driven process (only in theory).

The outlet volume (flow rate) and outlet pressure are determined by the length and diameter of the rotor. The longer the rotor is, the higher the pressure. The bigger the diameter of the rotor is, the faster the flow rate.

The notch of the spiral rotor is filled with air when it passes through the air inlet port. The notch is enclosed by the cabinet wall to form a compressed chamber when the rotor rotates. After the enclosure of the notch, lubricating oil is injected to seal, cool and lubricate the compressed chamber. The volume of the compressed chamber will be decreased when the rotor rotates and compresses the lubricant and air (gas-oil mixture for short) to compress the gas-oil mixture toward the air outlet port. The gas-oil mixture is exhausted through the compressor when the compressed chamber passes through the air outlet port which completes the process of air inlet, transmission, compression and air outlet.

Each rotor of the compressor is borne by antifriction bearing which is fixed by the end cover near the rotating shaft. The air inlet is borne by roller bearing while the air outlet is borne by a pair of reliable taper roller bearings to fix the position of the rotors. The bearing chosen shall bear axial and radial load and provide minimum clearance for axial operation.

The working cycle of the compressor can be divided into four procedures, namely air inlet, transmission, compression and air outlet. Each pair of toothing gears completes the same working cycle in succession.

1. Process of Air Inlet

The side air inlet of the compressor shall be designed to make the compressed chamber fully inlet the air while the screw compressor is not equipped with air inlet and outlet valves and the air inlet is controlled by the switching of the adjusting valve. The groove between the main and assistant rotors shall reach the maximum when the rotor rotates to the open gap of the air inlet port. Under that condition, the air between the groove and air inlet port can be ventilated freely. The air in the groove is fully outlet and the groove is in the vacuum condition after the exhaustion. The air outside will be inlet to the groove between the main and assistant rotors along the axis when the rotor rotates to the air inlet port. The side surface of the air inlet deflects from the air inlet port of the cabinet when the whole groove is filled with air and the air between the grooves is enclosed.

2. Process of Enclosure and Transmission

The gear crest of the main and assistant rotors will be enclosed with the cabinet when the process of air inlet of these two rotors is completed. The air in the groove is enclosed which means the process of enclosure. The two rotors continue to rotate and the gear cabinet will be geared to the groove in the air inlet port and the geared surface gradually moves to the air outlet port.

3. Process of Compression and Oil Injection

The toothing surface gradually moves to the air outlet port during the process of transmission which means the groove between toothing surface and air outlet port is gradually diminished and the air in the groove is gradually compressed and the pressure is increased. This is the process of compression. Meanwhile, the lubricating oil is injected into the compressed chamber and mixed with the air due to the pressure difference.

4. Process of Air Outlet

The compressed air (with the highest pressure) begins to be outlet when the geared surface of the rotor meets the air outlet port of the cabinet until the toothing surface of gear crest and groove moves to the air outlet surface. At that time, the groove between the toothing surface of the two rotors and the air outlet of the cabinet is zero which means the process of air outlet is completed. Meanwhile, the length of toothing surface of the two rotors and the air inlet port of the cabinet reaches the maximum and it continues to inlet the air.

Screw compressor has the same working principle with the piston compressor, both of which belong to positive displacement compressors. Screw compressor has the following advantages in terms of the results:

1) High Reliability.

Screw compressors have fewer spare parts without any easily worn-out parts. It has a longer life span with reliable operation. The overhaul interval reaches 40,000-80,000 hours.

2) Easy Operation and Maintenance.

Screw compressors are highly robotized which means the operators do not need to have long-time professional training. Unguarded operation can be realized by the compressor.

3) Excellent Dynamic Balance

Screw compressors without imbalance inertia force runs smoothly at high speed to realize groundless operation which especially fit to work as portable compressor with the features of small volume, light weight and little floor area.

4) Great Flexibility

Screw compressors have the feature of compulsory air transmission whose flow rate of the volume is hardly affected by the pressure of air outlet. It keeps high working efficiency in a broader range and can be adapted to many working conditions with no need to change the structure of the compressor.

However, the existing screw compressors still have some disadvantages. The compressor always runs under the condition of low voltage (230V) or high voltage (460V). The shift from low voltage to high voltage is always realized by changing the connection mode of the compressor. In general practice, the compressor shall be reconnected. A new simple and easy operational method is needed because of the complex process of reconnection, time wasting and easy misconnection which are caused by too many wiring terminals.

China Patent CN01144171.2 reveals a high and low voltage separator for scroll compressors. As for the scroll compressors whose refrigeration gases are compressed by the static and dynamic turbine disks in the sealed volume, convex plate is set at the end of the static turbine disk in the sealed volume and high-pressure chamber and low-pressure chamber are formed when the convex plate and the interior wall of the sealed volume are tightly coupled. The problem of complex wiring is not solved by the application of the invention.

China Patent CN200710187629.1 reveals a high and low voltage separator for scroll compressors which comprises the cabinet which forms the enclosed space, fixed scroll which plugs into the cabinet and coupled with rotating scroll to form a pressure chamber which divides the internal space of the cabinet into air inlet space and air outlet space, and at least one sealing spare part to seal the inside peripheral surface of the cabinet and the outside peripheral surface of fixed scroll. The problem of complex wiring is either not solved by the application of the invention

SUMMARY OF THE INVENTION

The technical problem to be solved by the invention is to easily realize the shift between high and low voltage as well as power frequency and frequency conversion of the compressor through an electrical control system.

In addition, the invention provides the electrical control method of said electrical control system.

The following technical plan is adopted by the invention to solve the above-mentioned technical problems:

A screw compressor, wherein its electrical control system comprises a power module, a high-low (tension) transformer which connects said power module to provide at least two sets of different voltages, namely the first voltage and the second voltage.

A screw compressor wiring control circuit connects said high-low (tension) transformer to control the switching of said wiring terminals and the connection mode.

Said screw compressor wiring control circuit controls the switching of said wiring terminals and the connection mode by a connecting unit. When the first voltage is connected to the screw compressor, the connecting circuit formed by said wiring terminals which are controlled by said connecting unit will be in the first status. When the second voltage is connected to the screw compressor, the connecting circuit formed by the wiring terminals which are controlled by said connecting unit will be in the second status. Furthermore, the machine winding is in parallel by said connecting unit when the low voltage is connected to the compressor and it is in series by said connecting unit when the high voltage is connected.

As an optimized plan of the invention, said electrical system comprises a frequency converter to control said compressor in the status of frequency conversion and said frequency converter is controlled by a control circuit.

As an optimized plan of the invention, said wiring terminals connect machine winding; said connecting units control the switching of said wiring terminals and the connection mode to further control that of the machine winding; The machine winding is in parallel by said connecting unit When the first voltage is connected to the screw compressor; The machine winding is in series by said connecting unit when the second voltage is connected.

As an optimized plan of the invention, said connecting unit is a jumper through which the switching of said wiring terminals of the compressor and the connection mode are controlled.

As an optimized plan of the invention, the machine winding is in parallel by said connecting unit when the first voltage is connected to the screw compressor; the wiring terminals of the compressor are short connected in a pair wise way by the jumper, namely U1 and U5, U2 and U6, V1 and V5, V2 and V6, W1 and W5, W2 and W6, among which U1 connects the signal of Ua, U6 connects the signal of Ub, V1 connects the signal of Va, V6 connects the signal of Vb, W1 connects the signal of Wa, W6 connects the signal of Wb.

As an optimized plan of the invention, the wiring terminals of the screw compressor, namely U1 and U5, U2 and U6, V1 and V5, V2 and V6, W1 and W5, W2 and W6 shall be short connected by some jumpers; meanwhile, the spacers shall be set between U5 and U2, V5 and V2, W5 and W2. Said jumpers and spacers shall be set in an integrated way according to the positions of the wiring terminals of the screw compressor.

As an optimized plan of the invention, the wiring terminals U5 and U2, V5 and V2, W5 and W2 shall be short connected by the jumpers when second voltage is connected to the compressor. Said jumpers shall be set in an integrated way according to the positions of the wiring terminals of the screw compressor.

As an optimized plan of the invention, said electrical control system comprises some relays which are respectively controlled by different control circuits.

As an optimized plan of the invention, said electrical control system also comprises via circuit which is set between said power module and high-low (tension) transformer; said electrical control system comprises a safing circuit between said power module and high-low (tension) transformer.

As an optimized plan of the invention, the inlet terminals of the said high-low (tension) transformer, No. 4 connects No. 6 and No. 1 connects No. 6, then the transformer outlets the first voltage; the inlet terminals of the said high-low (tension) transformer, No. 1 connects No. 6, then the transformer outlets the second voltage; said first voltage is low voltage and said second voltage is high voltage.

The above-mentioned electrical control methods control the switching of said wiring terminals and the connection mode through a connecting unit; the wiring circuit formed by said wiring terminals of the connecting unit is in the first status when the first voltage is connected to the screw compressor and it is in the second status when the second voltage is connected;

As an optimized plan of the invention, said electrical control system comprises a frequency converter to control said compressor in the status of frequency conversion and said frequency converter is controlled by a control circuit.

As an optimized plan of the invention, said wiring terminals connect machine winding; said connecting units control the switching of said wiring terminals and the connection mode to further control that of the machine winding; The machine winding is in parallel by said connecting unit when the first voltage is connected to the screw compressor; The machine winding is in series by said connecting unit when the second voltage is connected.

As an optimized plan of the invention, said connecting unit is a jumper through which the switching of said wiring terminals of the compressor and the connection mode are controlled.

As an optimized plan of the invention, the machine winding is in parallel by said connecting unit when the first voltage is connected to the screw compressor; the wiring terminals of the compressor are short connected in a pair wise way by the jumper.

As an optimized plan of the invention, said methods involve the procedures of replacing motors with different specifications.

The beneficial effects of the invention are that the electrical control system of the compressor revealed by the invention can easily realize the switching of low and high voltage by changing the jumpers on the wiring terminals of the patch board with no need to change the connection mode of the motor. The invention with its simple structure effectively avoids the niggling jobs of shifting between high and low voltage of the compressor. In addition, the invention realizes the shift between power frequency and frequency conversion of the compressor.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is the circuit diagram of the electrical control system of the invented compressor.

FIG. 2 is the sketch map of the connection of high and low voltage compressor wiring terminals.

FIG. 3 is the schematic diagram of shifting from power frequency to frequency conversion in single voltage.

FIG. 4 is the schematic diagram of shifting between power frequency and frequency conversion in dual voltage.

FIG. 5 is the sketch map of the connection of compressor wiring terminals in power frequency.

FIG. 6 is the sketch map of the connection of compressor wiring terminals in frequency conversion.

FIGS. 7-1 and 7-2 are sketch maps of machine winding connection in low voltage.

FIGS. 8-1 and 8-2 are sketch maps of machine winding connection in high voltage.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The optimized embodiment of the present invention are described as follows in detail in combination with the attached figures.

Embodiment 1

Please refer to FIG. 1. The present invention reveals a compressor electric control system, which includes a power module, a high-low tension transformer and a compressor wiring control circuit. The high-low tension transformer connects the above-mentioned power module to provide at least two-sets of different voltages, namely the first voltage (low voltage) and the second voltage (high voltage). The compressor wiring control circuit connects the above-mentioned high-low tension transformer to control the switching of the various wiring terminals and the connection mode of the compressor. When the first voltage is connected to the compressor, the wiring circuit formed by wiring terminals which are controlled by the above-mentioned connecting unit will be in the first status. When the second voltage is connected to the compressor, the connecting circuit formed by wiring terminals which are controlled by the above-mentioned connecting unit will be in the second status.

As shown in FIG. 1, in this embodiment, the compressor system includes main motor and fan motor. Main motor is connected with the high-low tension transformer KB through the wiring terminal TB3, and fan motor connected with the high-low tension transformer KB through the wiring terminal T134. The present invention changes the connection status of various terminals in the wiring terminal 1B3 by means of jumpers.

Concretely as shown in FIG. 1, three-phase supply L1, L2 and L3 are firstly connected to a safing circuit QF. Then electric current is divided into two ways by a via circuit. The first way is connected with the high-low tension transformer KB, compressor controller MAM and fan motor, and the second way with main motor through the current transformer CT1, relay KM1, relay KM2 and wiring terminal TB3.

The above-mentioned first way three-phase currents are connected to the fan motor through relay. KM4, thermal relay FR2 and wiring terminal TB4. The above-mentioned first way three-phase current respectively pass through fuse FU1, FU2 and FU3. One way is connected to port 13, 15 and 17 (port 13, 15 and 17 respectively correspond to signal Ua, Ub and Uc) of the above-mentioned compressor controller MAM, and the other way connected to the above-mentioned high-low tension transformer KB.

The port 1, 2 and 3 of the compressor controller MAM are connected with the three-phase supply provided by the current transformer CT1. Then 220V standard voltage is formed at port 25 and 26 of the compressor controller MAM. The high-low tension transformer KB can convert the voltage into 230V low voltage or 460V high voltage as required. The port 18, 20, 21 and 22 of the compressor controller MAM respectively control the switches of relay KM4, relay KM1, relay KM3, relay KM2.

The above-mentioned second way three-phase current is connected with main motor through the current transformer CT1 and wiring terminal TB3. Through the current transformer CT1, the electric current is divided into two ways. One way (Ua, Va, Wa) is connected to the wiring terminal TB3 through relay KM1 and thermal relay FR1 and then connected to the first group port of main motor; the other way (Ub, Vb, Wb) is connected to the wiring terminal TB3 through relay KM2 and then connected to the second group port of main motor. When main motor is used under high voltage or low voltage, it needs to select the connection mode between the above-mentioned high-low tension transformer KB and main motor by means of the wiring terminal TB3.

Please refer to FIG. 2, FIG. 7-1 and FIG. 7-2. When the low voltage (230v) wiring is used for the compressor connecting mode, it only needs to make No. 4 input terminal and No. 6 input terminal of the transformer short connected and make No. 1 input terminal and No. 6 input terminal short connected. Then various terminals of main motor wiring terminal are respectively short connected by jumpers two by two to ensure that the control machine winding of the above-mentioned connecting unit is in parallel. Namely terminal U1 and U5 are short connected; U2 and U6 short connected; V1 and V5 short connected; V2 and V6 short connected; W1 and W5 short connected; W2 and W6 short connected; hereinto, terminal U1 is connected to signal Ua; terminal U6 connected to signal Ub; terminal V1 connected to signal Va; terminal V6 connected to signal Vb; terminal W1 connected to signal Wa; and terminal W6 connected to signal Wb. Meanwhile, small spacers are set between terminal U5 and U2, between terminal V5 and V2, between terminal W5 and W2. Herefrom the compressor runs in low voltage (230V) status.

Please refer to FIG. 8-1 and FIG. 8-2. When the compressor connecting mode is changed from low voltage (230v) to high voltage (460v), it only needs to make No. 1 and No. 6 input terminals of the transformer short connected (remove the jumper between No. 4 input terminal and No. 6 input terminal). Later it only needs to change the jumper of terminals instead of changing the connection mode of the compressor. As shown in FIG. 2, terminal U5 and U2 of the wiring terminal TB3 are short connected; terminal V5 and V2 short connected; and terminal W5 and W2 short connected by the jumpers to ensure that the control machine winding of the above-mentioned connecting unit is in series.

In addition, the present invention also includes the procedure of replacing the motor with different specification. The interchange of dual motor specifications can be realized only by replacing the motor.

To sum up, inter-conversion between high and low voltages can be realized conveniently only by changing the jumper on patch board terminals in the compressor electric control system revealed in the present invention, while the connecting mode of the compressor need not be changed. The present invention is simple in structure, effectively avoiding trivial work during conversion between high and low voltages of the compressor.

Embodiment 2

The difference between this embodiment and Embodiment 1 lies in that this embodiment can conveniently realize mutual conversion between power frequency and frequency conversion.

Please refer to FIG. 3, which reveals a schematic diagram of mutual conversion between power frequency and frequency conversion of the compressor under single voltage. Three-phase supply L1, L2 and L3 are firstly connected with a sating circuit QF. Then electric current is divided into two ways by a via circuit TB. The first way is connected with frequency converter A1 and then connected with main motor through main motor wiring terminal TB3; the second way is connected with a via circuit TB 1, by which this way of electric current is divided into two ways (the second-first way and the second-second way). The second-first way is connected with main motor through the current transformer CT1, relay KM1, relay KM2 and wiring terminal T133; the second-second way is connected with the fan motor, transformer and compressor controller KY02S.

The above-mentioned first way three-phase current is connected with frequency converter A1 and then connected with main motor through relay KM5 and main motor wiring terminal TB3. The frequency converter A1 is used to control the above-mentioned compressor and make it remain at the frequency conversion working order. The port E, COM and AI2 of the above-mentioned frequency converter A1 are connected with port 13 and 21 of the above-mentioned compressor controller KY02S. The above-mentioned frequency converter A1 is controlled by the compressor controller KY02S.

The second-first way three-phase current above-mentioned is connected to the current transformer CT1 above-mentioned. The port a, b and c of the current transformer CT1 are connected to port 1, 2 and 3 of compressor controller KY02S. The second-first way three-phase current is divide into two ways by the current transformer CT1 above-mentioned. One way is connected to the wiring terminal TB3 through relay KM1, and the other way connected to the wiring terminal TB3 through relay KM2 and then connected to main motor through the wiring terminal TB3.

The second-second way three-phase current above-mentioned is connected to the current transformer CT2 (The port a, b and c of current transformer CT2 are connected to port 4, 5 and 6 of compressor controller KY02S) and then connected to the above-mentioned fan motor through relay KM4. Meanwhile, after the second-second way three-phase current above-mentioned respectively pass through fuse FU1, FU2 and FU3, one way is connected to port 23, 24 and 25 of the above-mentioned compressor controller KY02S, and the other way connected to the above-mentioned transformer KB. The port 27, 28, 29, 31 and 34 of compressor controller KY02S respectively control the switches of relay KM1, KM3, KM2, KM4 and KM5.

When the compressor needs mutual conversion between power frequency and frequency conversion, it only needs to change the connecting mode between relay KM1, KM2, KM5 and compressor wiring terminal, which can be controlled by compressor controller KY02S.

When the compressor runs in power frequency, please refer to FIG. 5 for terminal connection. The port 211 of relay KM1 is connected to terminal T1 of main motor; the port 4T2 connected to terminal T2 of main motor; the port 6T3 of relay KM1 connected to terminal T3 of main motor; the port 2T1 of relay KM2 connected to terminal T6 of main motor; the port 4T2 of relay KM2 connected to terminal T4 of main motor; and the port 6T3 of relay KM2 connected to terminal T5 of main motor.

When the compressor runs in frequency conversion, please refer to FIG. 6 for terminal connection. The port 2T1 of relay KM5 is connected to terminal T1 and T6 of main motor; the port 4T2 of relay KM5 connected to terminal T2 and T4 of main motor; and the port 6T3 of relay KM5 connected to terminal T3 and T5 of main motor.

To sum up, in the present invention, electric control system of the compressor in the single voltage work environment can be mutually converted between power frequency and frequency conversion.

Embodiment 3

The difference between this embodiment and Embodiment 2 lies in that the compressor in this embodiment works in the dual voltage environment.

Please refer to FIG. 4, it reveals a schematic diagram of mutual conversion between power frequency and frequency conversion of the compressor under dual voltage. The three-phase supply L1, L2 and L3 are firstly connected to a safing circuit QF and then is divided into two ways by the via circuit TB; The first way is connected to frequency converter A1 and then connected to main motor through wiring terminal TB3 of main motor; the second way is connected to a via circuit TB1, by which this way of electric current is divided into two ways (the second-first way and the second-second way) The second-first way is connected with main motor through current transformer CT1, relay KM1, relay KM2 and wiring terminal TB3, and the second-second way connected with the fan motor, high-low tension transformer KB and compressor controller KY02S.

The above-mentioned first way three-phase current is connected with frequency converter A1 and then connected with main motor through relay KM5 and main motor wiring terminal TB3. The frequency converter A1 is used to control the above-mentioned compressor and make it remain at frequency conversion working order. The port E, COM and AI2 of the above-mentioned frequency converter A1 are connected with port 13 and 21 of the above-mentioned compressor controller KY02S. The above-mentioned frequency converter A1 is controlled by the compressor controller KY02S.

The second-first way three-phase current above-mentioned is connected to the above-mentioned current transformer CT1. The port a, b and c of current transformer CT1 are connected to port 1, 2 and 3 of compressor controller KY02S. The second-first way three-phase current is divide into two ways by the current transformer CT1. One way is connected to the wiring terminal TB3 through relay KM1, and the other way connected to the wiring terminal TB3 through relay KM2 and then connected to main motor through the wiring terminal TB3.

The second-second way three-phase current above-mentioned is connected to the current transformer CT2 (The port a, b and c of current transformer CT2 are connected to port 4, 5 and 6 of compressor controller KY02S) and then connected to the above-mentioned fan motor through relay KM4. Meanwhile, after the second-second way three-phase current respectively pass through fuse FU1, FU2 and FU3, one way is connected to port 23, 24 and 25 of the above-mentioned compressor controller KY02S, and the other way connected to the above-mentioned high-lower tension transformer KB. The high-low tension transformer KB can convert the voltage into 230V low voltage or 460V high voltage as required. The port 27, 28, 29, 31 and 34 of compressor controller KY02S respectively control the switches of relay KM1, relay KM3, relay KM2, relay KM4 and relay KM5.

When the compressor needs mutual conversion between power frequency and frequency conversion, it only needs to change the connecting mode between relay KM1, KM2, KM5 and compressor wiring terminal, which can be controlled by compressor controller KY02S.

When the compressor runs in power frequency, please refer to FIG. 5 for terminal connection. The port 211 of relay KM1 is connected to terminal T1 of main motor; the port 4T2 of relay KM1 connected to terminal T2 of main motor; and the port 6T3 of relay KM1 connected to terminal T3 of main motor. The port 2T1 of relay KM2 is connected to terminal T6 of main motor; the port 412 of relay KM2 connected to terminal T4 of main motor; and the port 613 of relay KM2 connected to terminal T5 of main motor.

When the compressor runs in frequency conversion, please refer to FIG. 6 for terminal connection. The port 2T1 of relay KM5 is connected to terminal T1 and T6 of main motor; the port 412 of relay KM5 connected to terminal T2 and T4 of main motor; and the port 6T3 of relay KM5 connected to terminal T3 and T5 of main motor,

The inter-conversion process between high and low voltages in this embodiment is the same as Embodiment 1.

Please refer to FIG. 2. When the low voltage (230v) wiring is used for the compressor connecting mode, it only needs to make No. 4 and No. 6 input terminals of the transformer short connected and make No. 1 and No. 6 input terminals short connected. Then various terminals of main motor wiring terminal are respectively short connected by jumpers two by two, namely terminal U1 and U5 are short connected; U2 and U6 short connected; terminal V1 and V5 short connected; V2 and V6 short connected; terminal W1 and W5 short connected; W2 and W6 short connected; Thereinto, terminal U1 is connected to signal Ua; terminal U6 connected to signal Ub; terminal V1 connected to signal Va; terminal V6 connected to signal Vb; terminal W1 connected to signal Wa; and terminal W6 connected to signal Wb. Meanwhile, small spacers are set between terminal U5 and U2, between terminal V5 and V2, and between terminal W5 and W2. Herefrom the compressor runs in low voltage (230V) status.

When the compressor connecting mode is changed from low voltage (230v) to high voltage (460v), it only needs to make No. 1 and No. 6 input terminals of the transformer short connected (remove the jumper between No. 4 and No. 6 input terminals). Later it only needs to change the jumper of terminals instead of changing the connection mode of the compressor. As shown in FIG. 2, by means of the jumpers, terminal U5 and U2 of the wiring terminal TB3 are short connected; terminal V5 and V2 short connected; terminal W5 and W2 short connected.

To sum up, in the present invention, electric control system of the compressor in dual voltage (such as 230V and 460 V) work environment can be mutually converted between power frequency and frequency conversion. Meanwhile, in the present invention, inter-conversion between high and low voltages can be realized conveniently only by changing the jumpers on patch board terminals, while the connecting mode of the compressor need not be changed. The present invention is simple in structure, effectively avoiding trivial work during high-low tension conversion of the compressor.

Embodiment 4

The difference between this embodiment and Embodiment 1 lies in that when the low voltage (230v) wiring is used for the compressor connecting mode, it only needs to make No. 4 and No. 6 input terminals of the transformer short connected and make No. 1 and No. 6 input terminals short connected. Then various terminals of compressor wiring terminal are respectively short connected by jumpers two by two to ensure that the control machine winding of the above-mentioned connecting unit is in parallel, namely terminal U1 and U5 are short connected; U2 and U6 short connected; terminal V1 and V5 short connected; V2 and V6 short connected; terminal W1 and W5 short connected; W2 and W6 short connected; Thereinto, terminal U1 is connected to signal Ua; terminal U6 connected to signal Ub; terminal V1 connected to signal Va; terminal V6 connected to signal Vb; terminal W1 connected to signal Wa; and terminal W6 connected to signal Wb. Meanwhile, small spacers are set between terminal U5 and U2, between terminal V5 and V2, and between terminal W5 and W2. The difference between this embodiment and Embodiment 1 lies in that in this embodiment, various jumpers and small spacers above-mentioned are set as one according to various terminal positions.

When the compressor connection mode is changed from low voltage (230v) to high voltage (460v), it only needs to make No. 1 and No. 6 input terminals of the transformer short connected (remove the jumper between No. 4 and No. 6 input terminals). Later it only needs to change the jumper of terminals instead of changing the connection mode of the compressor. As shown in FIG. 2, terminal U5 and U2 of the wiring terminal TB3 of the compressor are short connected; terminal V5 and V2 short connected; terminal W5 and W2 short connected by the jumpers to ensure that the control machine winding of the above-mentioned connecting unit is in series. In this embodiment, various jumpers above-mentioned are set as one according to various terminal positions.

In this embodiment, connection between the jumper and compressor wiring terminal is more convenient by setting various jumpers (or including small spacers) as one. It can be short connected on ly by setting at one time.

Embodiment 5

When low voltage (230v) wiring is used for the compressor connecting mode, various terminals of the compressor wiring terminal are not limited to the short connected mode two by two in sequence and can adopt other connecting modes. In addition, when high voltage (460v) wiring is used for the compressor connecting mode, various terminals of the compressor wiring terminal can also adopt other connecting modes. It only needs to meet the following conditions: When low voltage is connected to the compressor, the control machine winding of the above-mentioned connecting unit is in parallel; when high voltage is connected to the compressor, the control machine winding of the above-mentioned connecting unit is in series.

Embodiment 6

The difference between this embodiment and Embodiment 1 lies in that the mentioned compressor can be any other types of compressors except the screw compressor, such as other types of positive-displacement compressor, or reciprocating compressor and centrifugal compressor.

The description and application of the invention is illustrative and application scope is not restricted in the above-mentioned cases. Both deformation and changes are possible in the disclosed cases. It is known to all the ordinary technicians that the cases shall be replaced and different spare parts have the same results. It shall be clear for the technicians in this field that the invention can be realized in other forms, structures, layouts, proportions with other spare parts, materials and components under the condition that the spirit and the essence of the invention are not deviated. Other deformation and changes can be adopted in the disclosed cases under the condition that the spirit and the scope of the invention are not deviated. 

1. A screw compressor, wherein its electrical control system comprises a power module, a high-low (tension) transformer which connects said power module to provide at least two sets of different voltages, namely the first voltage and the second voltage. a screw compressor wiring control circuit connects said high-low (tension) transformer to control the switching of said wiring terminals and the connection mode. said screw compressor wiring control circuit controls the switching of said wiring terminals and the connection mode by a connecting unit. When the first voltage is connected to the screw compressor, the connecting circuit formed by said wiring terminals which are controlled by said connecting unit will be in the first status. When the second voltage is connected to the screw compressor, the connecting circuit formed by the wiring terminals which are controlled by said connecting unit will be in the second status.
 2. The screw compressor according to claim 1, wherein said electrical control system comprises a frequency converter to control said compressor in the status of frequency conversion and said frequency converter is controlled by a control circuit.
 3. The screw compressor according to claim 1, wherein said wiring terminals connect machine winding; said connecting units control the switching of said wiring terminals and the connection mode to further control that of the machine winding; The machine winding is in parallel by said connecting unit when the first voltage is connected to the screw compressor; The machine winding is in series by said connecting unit when the second voltage is connected.
 4. The screw compressor according to claim 3, wherein the machine winding is in parallel by said connecting unit when the low voltage is connected to the compressor; the machine winding is in series winding by said connecting unit when the high voltage is connected.
 5. The screw compressor according to claim 1, wherein said connecting unit is a jumper, then the switching of said wiring terminals of the compressor and the connection mode are controlled by the jumper.
 6. The screw compressor according to claim 5, wherein the machine winding is in parallel by said connecting unit when the first voltage is connected to the screw compressor; the wiring terminals of the compressor are short connected in a pairwise way by the jumper.
 7. The screw compressor according to claim 6, wherein said wiring terminals of the compressor are short connected, namely U1 and U5, U2 and U6, V1 and V5, V2 and V6, W1 and W5, W2 and W6, among which U1 connects the signal of Ua, U6 connects the signal of Ub, V1 connects the signal of Va, V6 connects the signal of Vb, W1 connects the signal of Wa, W6 connects the signal of Wb.
 8. The screw compressor according to claim 7, wherein the wiring terminals of the screw compressor, namely U1 and U5, U2 and U6, V1 and V5, V2 and V6, W1 and W5, W2 and W6 shall be short connected by some jumpers; meanwhile, the spacers shall be set between U5 and U2, V5 and V2, W5 and W2.
 9. The screw compressor according to claim 8, wherein said jumpers and spacers shall be set in an integrated way according to the positions of the wiring terminals of the screw compressor.
 10. The screw compressor according to claim 7, wherein the wiring terminals U5 and U2, V5 and V2, W5 and W2 shall be short connected by the jumpers when second voltage is connected to the compressor.
 11. The screw compressor according to claim 10, wherein said jumpers shall be set in an integrated way according to the positions of the wiring terminals of the screw compressor.
 12. The screw compressor according to claim 1, wherein said electrical control system comprises some relays which are respectively controlled by different control circuits.
 13. The screw compressor according to claim 1, wherein said electrical control system also comprises via circuit which is set between said power module and high-low (tension) transformer; said electrical control system comprises a safing circuit between said power module and high-low (tension) transformer.
 14. The screw compressor according to claim 1, wherein the inlet terminals of the said high-low (tension) transformer, No. 4 connects No. 6 and No. 1 connects No. 6, then the transformer outlets the first voltage; the inlet terminals of the said high-low (tension) transformer, No. 1 connects No. 6, then the transformer outlets the second voltage; said first voltage is low voltage and said second voltage is high voltage.
 15. An electrical control method of a screw compressor according to any claims from 1, wherein said compressor wiring control circuit control the switching of said wiring terminals and the connection mode through a connecting unit; the wiring circuit formed by said wiring terminals of the connecting unit is in the first status when the first voltage is connected to the screw compressor and it is in the second status when the second voltage is connected;
 16. The electrical control method of a screw compressor according to claim 15, wherein said electrical control system comprises a frequency converter to control said compressor in the status of frequency conversion and said frequency converter is controlled by a control circuit.
 17. The electrical control method of a screw compressor according to claim 15, wherein said wiring terminals connect machine winding; said connecting units control the switching of said wiring terminals and the connection mode to further control that of the machine winding; The machine winding is in parallel by said connecting unit when the first voltage is connected to the screw compressor; The machine winding is in series by said connecting unit when the second voltage is connected.
 18. The electrical control method of a screw compressor according to claim 15, wherein said connecting unit is a jumper through which the switching of said wiring terminals of the compressor and the connection mode are controlled.
 19. The electrical control method of a screw compressor according to claim 15, wherein the machine winding is in parallel by said connecting unit when the first voltage is connected to the screw compressor; the wiring terminals of the compressor are short connected in a pairwise way by the jumper.
 20. The electrical control method of a screw compressor according to claim 15, wherein said methods involve the procedures of replacing motors with different specifications. 